Updated from 8:22 a.m. EDT to include CEO comments. 

Investors cheering McDonald's (MCD - Get Report) better-than-expected third-quarter results may want to relax a bit. 

Shares of the Golden Arches rose as much as 3.5% in premarket trading Friday as adjusted earnings came in at $1.62 a share, beating Wall Street forecasts for $1.49. McDonald's continued to see profits helped by cost cuts and efforts to re-franchise restaurants around the world, which helped lower expenses. Total revenue amounted to $6.42 billion, surpassing analysts' expectations for $6.28 billion. 

But sales at McDonald's all-important U.S. business continued to slow amid people choosing to eat at home due to falling grocery store prices and stepped up promotions by other fast-food concepts. McDonald's U.S. sales rose 1.3%, relatively in line with analyst estimates, but a slower pace than the 1.8% increase seen in the second quarter. In the first quarter, McDonald's U.S. same-store sales rose 5.4%.

"We are mindful of the headwinds, most notably in the U.S.," McDonald's CEO Steve Easterbrook told analysts on a call. 

The results were even more disappointing considering McDonald's aggressive TV marketing of its new Chicken Nuggets, made without artificial ingredients, during the Olympics and steady stream of ads for its all-day breakfast platform. As a result of the slowdown and tough year-ago comparisons, McDonald's may be on track to show a decline in sales in the U.S. for the fourth quarter. 

"Investors are well prepared for a return to negative same-store sales in the fourth quarter," said analysts at Barclays in a recent note. 

Meanwhile, McDonald's repurchased an eye-popping 23.3 million shares of stock for $2.7 billion during the quarter, which had the effect of propping up earnings due to a lower number of shares outstanding.